. The Bell System technical journal . THE VODAS 463 operation. When the armature of relay TM reaches its left-handcontact, relay Hi operates and delays release of the relay train even ifTM is at once restored to normal. Hi is delayed in releasing by thetime required to charge condenser Ci. The final release of relays 1and 4 is then controlled by the time constant of an auxiliary circuitinvolving relay H2 and condenser C2, while that of relays 2 and 5,which is made later so as to suppress delayed echoes, is controlled bythe circuit charging C3. On the receiving side, condenser C4 is ad-justable
. The Bell System technical journal . THE VODAS 463 operation. When the armature of relay TM reaches its left-handcontact, relay Hi operates and delays release of the relay train even ifTM is at once restored to normal. Hi is delayed in releasing by thetime required to charge condenser Ci. The final release of relays 1and 4 is then controlled by the time constant of an auxiliary circuitinvolving relay H2 and condenser C2, while that of relays 2 and 5,which is made later so as to suppress delayed echoes, is controlled bythe circuit charging C3. On the receiving side, condenser C4 is ad-justable so as to permit the technical operator to select the shortestrelease time for suppressing the delayed echoes in a given land Fig. 4—Type A control terminal at San Francisco. The vodas control terminal of the A type ^ used at New York con-sists of a line of technical operating positions with cross-connections toother lines of equipment containing the delay units, repeaters, vodasamplifier-detectors and privacy apparatus. Figure 4 shows anarrangement of a single terminal at San Francisco. The control bayis placed between two line testing bays on the left and two trans-mission testing bays on the right of the operating lineup. The dis-tributing frame is in the center of the picture; and repeaters, ringersand privacy apparatus are shown at its left. At the extreme left isthe vodas bay. 464 BELL SYSTEM TECHNICAL JOURNAL Syllabic Vodas—Type B Control Terminal The desire for a cheaper control terminal than the Type A led tothe development of a second type, known as Type B, in which thevodas employs the same fundamental principles. In this vodas addedprotection against false operation from line noise is secured
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